Television relief picture system



C. C. LARSON ETAL TELEVISION RELIEF PICTURE SYSTEM Feb. 24, 1948.

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Filed larch 29, 1945' 2 Sheets-Sheet 1 3 I oum m 4 i I mwxi g muptzmz h 452915 513 52 22 056 $42 056v. $230; N on a INVENTORS CHRESTIAN C. LARSON Q 56 6 5a 25 5 22 025 23 3.2243 F F 2 wzj 4323.5: 3

w. 3 E 0 m E E. HALLMARK ATTORNEY F eb. 24, 1948.

Filed larch 29. 1945 2 Sheets-Shoot 2 55 M T LINE 5cm. -L WAVE GEN. :04

smc. PULSE 1 REcEwER SEPARATOR j 0 FIELD 30m. :02 i 4, WAVE GEN. $4 a 1 56- mp5 AME MULTIVIBRATOR \ol U U U U .j

VOLTAGE OR CURRENT INVENTORS CHRISTIAN C. LARSON ATTORNEY I Patented Feb. 24,1948.

TELEVISION RELIEF PICTURE SYSTEM Christian c. Larson and Clyde a. animal-arm Wayne, Ind., assignors, by mesne assignments, to Farnsworth Research Corporation, a cor- UNITED s'ra'ras PATENT; OFFICE poratlonot Indiana Application March 29, 1945. Serial No. 585,588

Claims. (01. lid-8.5)

oscopic television picture-systems of this type are,

complicated because they require two picture signal generating tubes for supplying-picture signals which can be converted into images giving a plastic impression of the object. A150, auxiliary means must be provided the observer of the re'- ceived television image to segregate the reproduced video signals in such a manner that each eyeor the observer-receives light information from one of thepicture. signal generating tubes only: It has, for instance, been sug ested to provide two picture signal generating tubes arranged in such a mannerthat alternate lines of the ob- .iect are scanned in succession by the two tubes. The picture signal reproducing tube comprises a special viewing screen arranged so that each eye or the observer. sees one ;s et of reconstructed image lines corresponding togthe picture signals developed by one 01 the picture signal generating tubes. An arrangement of this i type, issubject to the some criticism of utilizing complicated apparatus for eflecting a. stereoscopic reproduction instantaneous brightness of a selected elemental area of an object. An electrode is arranged toofthe object. Furthermore, the special viewing screen required for the television reproducing tube does not permit the reproduction of standard television images,

It is an object of the present invention. therefore, to provide a novel method of and system for transmitting and receiving television pictures in relief. I

Another object-of the invention is toprovide a novel system for transmittingand receiving an object or scenewhereby images; representative r the object are;alternatelyreproduced; in oppositetransparencies, the. images having a positive transparency being displaced withrespect to the images having a negative transparency.-

, A further object oithe invention isto providenovel means in a television transmitting system for derivinggroupsof picture signals'ot alter: nate positive and negative polarity tive of the object to bereproduced.

Inaccordance with the present invention there is provided in a televisionsystem a picture signal generating tube: havingaiphotosensitive cathode. The object to be transn'iitted is projected upon the cathode, and means are provided cooperating representawith the cathode for deriving picture signals representative of the object. Further means are provided for reversing the polarity of successive groups of picture signals at a predetermined frequency. v

a In accordance with a preferred embodiment of the invention a television system for transmittin relief pictures comprises a picture signal generating tube having an electron multiplier including.

a plurality of multiplier stages. Means are provided for passing at any instant an electron stream into the multiplier representative or the receive secondary electrons from the last stage or the multiplier. Apparatus is provided for periodically reversing the polarity o: the output signal which includes means for alternately driving the electrode to a potential so that secondaryelectrons from the last multiplier stage are col-- lected thereby and to a potential so that secondary electrons from the last stage are repelled 1 thereby. Thus, either thelast stage of the elec-..

tron multiplier or the electrode is made a collector of electrons. polarity derived from the last multiplier stage is periodically reversed in synchronism with the rate of change of the potential on the electrode,

and successive groups of picture signals of (iii-- ferent polarity may be derived from the last electron multiplier stage.

In accordance with'the invention there is i'urther provided a television system for transmitting and receivingrelietpictures'comprising a picture signal generating tube having-means for,

deriving picture signals representative of an object. Means are provided for reversing the polarity of successive groups oi signals at a predetermined frequency aswell as means for transmit-v ting the picture signals and for-receivingthe same. Further means are provided for repro-.

ducing the television picture in accordance with;

the groups or picture signals, thereby to obtain a picture with positive transparency when a group of signals of one polarity is reproducedand a}, succeeding picture-with, negative transparency when the succeeding groups of signalshavi'ng an opposite polarity from that of the first group is reproduced. Finally,. means are provided for placing the television pictnreswith'positive transpare'ncy with respect tothe television pictures-1 Hence, the reprov with negative transparency. duced pictures exhibit a. relief efl'ect.

taken in connection with the accompanying drawings, and its scopevrili be pointed out in the appended claims.

In this manner the signal;

For a better understanding of the invention, together with other and further obiects thereoi,; reference is made to the following description.

In the accompanying drawings:

Pig. 1 illustrates i television transmitting apf paratus including circuit connections hown mainly in block form and embodying the present invention;

Fig. 2 is a representation of two diflerent com- 1 posite video signals referred to in explaining the operation of the invention; and

Fig. 3 illustrates a television receiving apparatus including circuit connections shown in and an anode shield 3 provided with a scanning aperture 4. Electron multiplier 5 is located in shield 3 and includes a plurality of multiplier stages such as first stage 8 arranged to receive photoelectron passing through aperture 4, penultimate stage I and last multiplier stage 8. Electrode I9 is arranged between penultimate sta e I and last stage 8 for a purpose to be explained hereinafter.

For the purpose of projecting an optical image of the object to be transmitted, schematically indicated by arrow H on photoelectrode cathode 2, there is provided optical system l2. For developing in the plane of scanning aperture 4 an electron image of the emission from cathode 2, there is provided cylindrical coil ll surrounding tube I and energized by means of a suitable current source such as a battery, not shown in the drawing to avoid confusion, Operating voltage between cathode 2 and anode 3 is provided by a battery or other suitable voltage source not illustrated.

For deflecting the electron image in two directions across scanning aperture 4 in anode shield 3, there are provided line deflecting coil l4 and field deflecting coil l5. Deflecting coils i4 and I5 are energized by horizontal line scanning generator l6 and vertical line scanning generator II, respectively, both synchronized by synchronizing pulses developed in synchronizing and blanking pulse generator II which may be connected to a 60-cycle alternating current source as indicated. Horizontal-line scanning generator ls develops saw-tooth current waves at a frequency of, for example, 15,750 cycles per second, while vertical line scanning generator il develops similar waves at a field frequency of, for example, 60 cycles per second, thereby to produce a 525-line interlaced scanning pattern at a frame frequency of 30 cycles per second and an inter- 60 cycles per second. By reproducing groups of.

picture signals of alternate positive and negative polarity in a television picture reproducing tube in such a manner that the images having a positive transparency are displaced with respect to images having a negative transparency, a relief effect may be obtained. This is accomplished in accordance with the present invention by alte natelyreversing or keying the potential sup-j plied to electrode Ill.

For the purpose providing operatingpotentials to the multiplier 5118383 01 electron multiplier there is provided battery connected to voltage divider 2i and having its positive terminal grounded as shown. Each of the stages of electron multiplier 5 is supplied with a potential that may, for instance, be 100 volts more positive than that of the preceding stage. The last multiplier stage 8 is kept at ground potential by lead 22 connected to a tap of potentiometer 2! through resistor 28. Lead 24 i connected to the same tap of potentiometer 2| through resistor 25 for normally keeping electrode-Ill at the same potential as stage 8. v Multiplier stage 1, being the penultimate stage, may be kept at a potential of 100 volts' negative against ground by lead 25 connected to a tap of voltage divider 2i.

In accordance with the invention electrode ii! is keyed in such a manner that its potential is alternately maintained at an intermediate value between that of penultimate stage i and last stage 8 or made positive with respect to last multiplier stage 8. To this end there is provided keying pulse amplifier 21 connected to synchronizing and blanking pulse generator l8. Keying pulse amplifier 21 receives pulses of a frequency of cycles per second from synchronizing and pulse generator it. Usually, there is included a generator for generating pulses such as blanking pulses at a frequency of 30 cycles per second in synchronizing pulse generator 18, or else a blocking oscillator may be provided for that purpose. Pulses derived from synchronizing generator It at a frequency of 30 cycles per second are delivered to keying pulse amplifier 2'! where they are amplified and then impressed by leads 28 and 22 on electrode ID. We may,.for instance, assume that the pulses amplified by keying pulse amplifier 2'! and impressed upon electrode l0 4 have a maximum potential of 50 volts positive against ground for 1/60 of a second and then a minimum potential of volts negative against ground for a duration of 1/60 of a second. Thus, electrode ill will alternately assume a potential of +50 volts and -50 volts.

Multiplier stage 8 alternately acts as an electron multiplier and an electron collector as will be more fully explained; for convenience, however, electrode 8 will be referred to as last multiplier stage 8. When electrode II) has a voltage of 50 volts positive against ground, it will attract secondary electrons liberated from last multiplier stage 8. At this instant last multiplier stage 8 is an electron source, while electrode [0 acts as a.

collector of electrons and hence is an electron sink. When the potential of electrode I0 is now.

multiplier stage 8 alternately acts as the last mul- .tiplier stage and as the electron collector, and hence the output signal obtained from multiplier stage 8 will have a polarity that is periodically reversed in synchronism with the rate of change of the keying pulses supplied to electrode [0. Therefore, the polarity of the output signal willchange at a rate of cycles per second.

The video signal of a periodically reversed signal polarity is derived from multiplier stage 3.

pulses arealso applied from synchronizing and blanking pulse generator iii to amplifier and mixer 33 to develop in amplifier the convert-.

tional composite television signal comprising picture signals as well as blanking and synchronizing signals. To the output of amplifier and mixer 30 there is coupled transmitter 32 for transmitting the composite television signal modulated on a carrier wave.

The television transmitting system as de-" scribed provides means for periodically reversing the signal polarity of the picture signals. However, in order to obtain television relief pictures it is also necessary to displace the reproduced television images of positive transparency with respect to the images of negative transparency. This can be eiiected in different ways. It is, for instance. possible to key the horizontal synchronizing pulses so that the time delay between the beginning of each blanking pulse and the beginning of each synchronizing pulse changes at a predetermined frequency, such as the field irequency of 60 cycles. images of opposite transparencies may be efiected. An arrangement of this kind may ad vantageously be incorporated into the television transmitter.

To explain more clearly this change 02 the time time as illustrated, while the ordinateis repre-' sentative of the voltage or current of the signal. 5

Thus, a displacement of The composite television signal shown in.

The black level is shown by dotted line 35, while the white level is represented by dotted line 33'. Blanking signal 31! coincides with the black level, while the horizontal sychronizing signal 38 extends beyond the black level into a region commonly referred to as blacker-than-black. The video signal proper is indicated at M and represents the instantaneous brightness values of a horizontal strip of the object to be transmitted which at that instant is under scansion.

The distance or time delay 4i between the beginning of blanking signal 31 and the beginning of horizontal sychronizing signal 38 is equal to 1% of the line scanning frequency of 15,750 cycles per second. In accordance with the invention the distance between the beginning ofblanking signal 31 and the beginning of horizon-' tal synchronizing signal 38 is made larger during predetermined interval's as shown at 42 in the upper curve of Fig. 2. An increase of time delay 4| as shown at 42 has the effect that the scanning beam in the picture reproducing tube begins its scanning motion aftera longer time interval than when the scanning beam is controlled according to the standard horizontal-synchronizing pulses illustrated in the bottom section of Fig. 2. The

result is that when the image is reproduced under" the control of horizontal synchronizing signal 38 having a time delay 42, the image is displaced Apparatus for alternately changing the time" delay or the horizontal sychronizing signal with respect to the blanking signal referred to hereinabove is illustrated in Fig. 1. To this end time delay mechanism shown enclosed in dotted lines 45'is connected to synchronizing and blankingpulse generator II as well as tokeying pulse generator 21. The horizontal synchronizing signal derived irom generator It is connected by lead 43 to three-element vacuum tubes 4'! and 43. Vacuum tube includes cathode 50, grid ii and anode 52,- while tube 43 is provided with cathode ".Rgrid-N and anode 55. The horizontal synchronizing'signal is applied by lead 46 through coupling condensers i8 and 51 to the grids BI and 54 of tubes 41 and 43, respectively. Battery 58, having its .positiveterminal grounded, is'provlded for supplying a biasing voltage to grids BI and 54 which may-tor instance, amount to 60 volts negative against ground. To this end battery it is connected by lead through resistor ii to grid ll. whilelead 62 connects grid 54 through resistor 33 to battery 58.

Vacuumtubes 41 and-48 are alternately blocked by'means-"oria keying pulse derived from generator-21 through lead 84-. .Lead 64 is connected to cathode-ll oltube 41 which in turn is grounded through resistor 85 as shown. The keying pulses derived fronrgenerator 2! are also connected through lead-St andresistor 86 to grid 54 of tube 40. a We may assume that generator 21 delivers a pulse'of anamplitude of 50 volts positive for a duration of 1/60 ofa second and another pulse or equal duration having an amplitude of 50 volts. When a pulse of +50 volts is applied to grid 54,.it will reduce the normal grid bias of -60 volts to -10 volts which will permit current to flow through tube 481. The same pulse of +50 volts applied tocathode 50 will increase the effective grid bias of tube ll to volts, thus blocking tubeid'l. On the other hand, if a negative pulse of 50 volts is impressed upon grid 54, the grid bias of tube 48 now amounts to -l10 volts which" will block tube 48. The same pulse of '+50 volts'is also applied to cathode 50 of tube 41 which reduces the grid bias of that tube to 10 volts, thus making the tube conductive. It is assumed, ofcourse. that both tubes 41 and 48 are able to conductv space current when their grid bias voltage is 10 volts negative against the cathode.

Hence, the signal impressed upon tubes 41 and 48 from lead 46 is alternately conducted through tube 41 or tube 48, each tube being conductive for 1 a duration of 1/60 oi'a second corresponding to theafleld frequency whereafter each tube is blocked for the same length of time. The output of tube 41 is derived from lead 61 connected to anode 52. and the'output of tube 48 is obtained from lead it connected to anode 55. Lead 61 is coupled teatime delaynetwork 10 consisting of a plurality oi' -colls .ll' connected in series and condensers-l2 connected betweencoils II and ground.

The-output signal oftime delay network I0 is derivedyacross resistor- 13 connected to lead 14 which in turn is connected to synchronizing pulse generator it. Theoutput ofjtube 48 is derived across resistor-liaise connected to lead 14.

Thus. time delay network 10 alternately imparts a predetermined time delay to the horizontal' line synchronizing-pulses at a frequency of 60 cycles" persecond. It may be mentioned that while kering'generator 21 is synchronized by the blankingwpuises from generator i8, the signals controlled by time delay mechanism so are the horizontal synchronizing pulses derived from generator I9. As explained hereinabove in connection with Fig. 2, the periodic timedelay of horizontal synchronizing signal 99 may be used for displacing the images reproduced during a1- ternate fields. The television transmitter illustrated in Fig. 1 may be used in connection with a conventional television receiver, the operation of which is well known to those skilled in the art.

The apparatus for displacing a reproduced television image of positive transparency with respect to the succeeding image of negative transparency, which has been described hereinabove, will effect a horizontal displacement of the positive and negative images with respect to each other. It is to be understood that alternate images corresponding to groups oi picture signals of opposite polarity may also be displaced in other directions. Thus, it is obvious that alternate images may be displaced in a vertical direction by keying the vertical line synchronizing pulses instead of keying the horizontal line synchronizing pulses by means of time delay mechanism Ali.v

The images of opposite transparency reproduced during alternate field cycles may also be displaced in another manner. This may be accomplished by keying the deflecting coil of a television picture reproducing tube in such a manner that the images of alternate fields are displaced with respect to each other. An arrangement of this kind is illustrated in Fig. 3 showing a television receiving station.

At the receiving station, receiver 99 amplifies and demodulates the received modulated carrier waves whereby the composite television signal containing groups of picture signals of opposite polarity is developed at the output terminals of receiver 99. This composite television signal is applied to control electrode 9! of cathode ray reproducing tube 92 to control the emission from cathode 93. Electrodes 94, 99 and 86, held at suitable operating potentials by battery 81 connected to voltage divider 89, develop an electron beam directed at fluorescent screen 99. This electron beam is scanned across fluorescent screen 99 in accordance with the 525-line interlaced scanning pattern by meansof the magnetic fields developed by deflecting coils 9i and 92 energized by line scanning wave generator 93 and field scanning wave generator 99, respectively. Scanning wave generators 93 and 94 are synchronized by scanning pulses obtained from synchronizing pulse separator 95 to the input of which the composite television signal is applied from receiver 89. Synchronizing pulse separator 95 is of conventional design and adapted to separate synchronizing signals from picture signals. The operation of the television receiver described is conventional and, therefore, no further explanation is deemed necessary here.

In accordance with the invention, horizontal deflecting coils 9|, connected to line scanning wave generator 99, are keyed at a frequency of 60 cycles per second corresponding to the field frequency and deflect the electron beam periodically over fluorescent screen 9. To this end differentiating amplifier 99 is connected to field scanning wave generator 94 which delivers a saw-tooth wave 91 at a frequency of 30 cycles per second to amplifier 99. Amplifier 99 differentiates saw-tooth wave 91 obtained from generator pulses I9I which are fed through lead I92 and resistor I93 to deflecting coils 9|. Condenser I94, connected between line I92 and ground as shown, provides a low impedance path to ground for the high frequency waves developed by generator 93.

By means of multivibrator I99 and lead I91 horizontal deflecting coils '9l are periodically supplied with a current pulse which develops a constant magnetic deflecting field which changes its strength during alternate field scanning cycles. The current pulses supplied by lead I92 to deflecting coils 9i are superimposed upon the current waves developed by line scanning wave generator 93 which cause the electron beam to sweep horizontally across fluorescent screen-99. Thus, images reproduced during alternate field scamiing cycles are displaced with respect to each other because all horizontal lines of one field are displaced with respect to the horizontal lines of the succeeding field. We may assume that receiver 99 receives successive groups of picture ceiver illustrated in Fig. 3 will operate in con- 94 and generates rectangular pulses 98 which are utilized for driving multivibrator I99. Multivibrator I99 develops symmetrical square wave junction with a television transmitter such as illustrated in Fig. 1 providing time delay mechanism 45 is omitted. On the other hand, if a television transmitter is provided which includes time delay mechanism such as illustrated at 45 in Fig. 1, no special keying means is required at the television receiver. In that case differentiating amplifier 99, multivibrator I99 and their associated networks may be omitted, and the television receiver will operate in the conventional manner.

The preferred way of reversing the signal polarity of alternate groups of picture signals is effected by means of an electron multiplier in the manner set forth hereinabove. A preferred apparatus for reversing the signal polarity has been illustrated in Fig. 1 in connection with an image dissector tube. However, the signal polarity may also be reversed in substantially the same manner as described herein by using any picture signal generating tube of the light storage type which utilizes an electron multiplier for amplifying the signal output. Pickup tubes of this type which employ electron multipliers are well known in the art and include, for instance, the orthicon where a low velocity electron beam is used for scanning a mosaic electrode.

It is further to be understood that the reversal of the signal polarity of alternate groups of picture signals may also be efiected in various ways other than by the utilization of an electron multiplier- For instance, it is feasible to derive video signals in any conventional manner, and to reverse the signal polarity periodically by alternately switching in and out a reversing amplifier. Switching of this nature may, for instance, be efiected by a keying mechanism similar to that shown enclosed by box 45. The reversing amplifier that is switched in and out at a predetermined frequency may add one more amplifier stage to the normally operative video amplifier chain. Since each amplifier stage reverses the output signal polarity. I

While there has been described what are t,

present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In a television system, a picture signal generating tube having a photosensitive cathode. means for projecting an object to the transmitted upon said cathode, an electron multiplier, means for scanning said cathode to pass at any instant an electron stream into-said multiplier representative of the instantaneous brightness of a selected elemental area of said object, said multiplier including a plurality of multiplier stages, and means for deriving successive groups of picture signals from the last stage of said multiplier, said groups of picture signals being representative of said object and of aipolarity means for reproducing the television picture in that is periodically reversed at a predetermined frequency. I

2. In a television system, a picture signal generating tube having an electron multiplier including a plurality of multiplier stages, means for passing at any instant an electron stream into said multiplier representative of the instantaneous brightness of a selected elemental area of an object, an electrode arranged to receive secondary electrons from the last stage of said multiplier, apparatus for periodically reversing the polarity of the output signal including means for alternately driving said electrode to a potential so that secondary electrons from said last stage are collected thereby and to a potential so that secondary electrons from saidlast stage are repelled thereby, and means for deriving successive groups of picture signals from said last stage of a polarity that is periodically reversed-in synchronism with the rate of change of the potential on saidelectrode. I

3. In a television system, a picture signal generating tube having an electron multiplier including a plurality of multiplier stages, means for passing at any instant an electron stream into said multiplier representative of the instantaneous brightness of a selected elemental area of an object, means for supplying each of said stages with a potential that is positive with respect to that of the preceding stage, an electrode arranged to receive secondary electrons from the last stage of said multiplier, apparatus for periodically reversing the polarity of the output signal including means for alternately driving said electrode to a potential that is between that of said last stage and that of the penultimate stage to repel secondary electrons from said last stage by said electrode and to a potential that is more positive than that of said last stage thereby to obtain a picture with positive transparency when a group of signals of one polarity is reproduced and a succeeding picture with negative transparency'when the succeeding group of signals having the opposite polarity from that of said first group is reproduced, and means for displacing said television pictures with positive transparency with respect to said television pictures with negative transparency, thereby to obtain a relief eflect of the reproduced picture.

5. In a television system for transmitting and receiving relief pictures, a cathcde ray picture reproducing tube including means for developing an electron beam and a target adapted to be scanned by said beam, means for controlling said beam in accordance with received groups of picture signals representative of the object to be reproduced, each of saidgroups having a signal polarity that is opposite from that of the succeeding group, means for deflecting said beam across said target in accordance with cyclically recurring scanning field patterns to produce a luminous image, and means for displacing the image representative of a group of picture signals of one polarity with respect to the image representative of the succeeding group of picture signals of opposite polarity, thereby to obtain a relief eflect of the reproduced picture.

6. In a' television system for transmitting and receiving relief pictures, a cathode ray picture reproducing tube including means for developing an electron beam and a target adapted to be scanned by said beam, means for controlling said beam in accordance with received groups of picture signals representative of the object to be reproduced, each of said groups having a signal Y polarity that is opposite from that of the suc= ceeding group, means for deflecting said beam across said target in accordance with cyclically recurring scanning field patterns to produce a luminous image, said field patterns being synchronized with said groups of picture signals, and means for displacing an image representative of a group of picture signals of one polarity with respect to an image representative of the succeeding group of picture signals of opposite polarity, thereby to obtain a relief effect of the reproduced picture.

7. In a television system for transmitting and receiving relief pictures, a cathode ray picture to collect secondary electrons from said last stage by said electrode, and means for deriving successive groups of picture signals from said last stage-of a polarity that is periodically reversed in synchronism with the rate of change of the poten tial on said electrode. a

4. A television system for transmitting and receiving relief pictures comprising a picture signal generating tube having means for deriving picture signals representative of an object, means for reversing the polarity of successive groups of said picture signals at a predetermined frequency, means for transmitting said picture signals, means for receiving said picture signals,

reproducing tube including means for developing an electron beam and a target adapted to be scanned by said beam, means for controlling said beam in accordance with received groups of picture signals representative of the object to be reproduced, each of said groups having ..a signal polarity that is opposite from that of the succeeding group, means for deflecting said beam across said target in accordance with cyclically recurring scanning field patterns to produce a,

luminous image, said field patterns being synchronized wlth'saidgroups of picture signals, and means associated with said deflecting means for periodically displacing an image representative of a group of picture signals of one polarity with respect to an image representative of the succeeding group of picture signals of opposite polarity, thereby to obtain a relief effect of the reproduced picture.

8. In a television system for transmitting and receiving relief pictures, a cathode ray picture reproducing tube including means for developing an electron beam and a-target adapted'to be l1 scanned by said beam, means for controlling said beam in accordance with received groups of picture signals representative of the object. to be reproduced, each of said-groups having a signal polarity that is oppositefrom that oi the succeeding group, means including a keying device an electron beam and a target'adapted to be scanned by said beam, means for controlling said beam in accordance with received groups of picture signals representative of the object to be reproduced, each of said groups having a signal polarity that is opposite from that of the succeeding group, means for deflecting said beam across said target in accordance with cyclically recurring scanning field patterns to produce a luminous image, and means including a keying device cooperating with said deflecting means for laterally shifting said beam in synchronism with the rate of change of said signal polarity, thereby to displace the image representative of a group of picture signals of one polarity with respect to the image representative of the succeeding group of picture signals of opposite polarity.

10. A television system for transmitting relief pictures including a picture signal generating tube having means for deriving picture signals representative of an object, means for reversing the polarity of successive groups of said picture signals at a predetermined frequency, means for developing synchronizing signals including pulses, means for developing a blanking signal including pulses, means for cyclically changing the time delay between the beginning of each pulse of said blanking signal and the beginning of each pulse of a selected one of said synchronizing signals in such a manner that said time delay changes in synchronism with the reversal of the polarity of said groups of picture signals, and'means for mixing said blanking and synchronizing signals with said groups of picture signals, thereby to derive a composite video signal output adapted for the reproduction of television pictures having a relief efiect representative of said object to be transmitted.

11. A television system for transmitting relief pictures including a picture signal generating tube having means for deriving picture signals representative of an object, means for reversing the polarity of successive groups of said picture signals at a predetermined frequency, means for developing a line synchronizing signal including pulses, means for developing a field synchronizing signal including pulses and having a lower frequency than said line synchronizing signal, means for developing a blanking signal including pulses of the same frequency as that of said line synchronizing signal, means for cyclically changing the time delay between the beginning of each pulse of said blanking signal and the beginning of each pulse of said line synchronizing signal in such a manner that said time delay remains unchanged during the transmis vgdeveloping a line synchronizing-signal including sion of each of said groups of picture signals and changes when the polarity of said groups of picture signals is reversed, and means for mixing said blanking and synchronizing signals with said groups of picture signals, thereby to derive a composite video signal output adapted 'for the reproduction of television pictures having a relief efiect representative of said object to be transmitted.

12. In a television system including a picture signal generating tube having a photosensitive member, an electronmultiplier having a plurality of multiplier stages and an electrode arranged to receive secondary electrons from the last stage of said multiplier, the method of transmitting television pictures which comprises the steps of projecting an optical image of the object to be transmitted on said photosensitive member, deriving an electron image representative of said object from said member, scanning "said electron image to direct at any instant an electron stream into said multiplier representative of the instantaneous brightness ofa selected elemental area of said image, alternately attracting secondary electrons from the last stageof said multiplier toward said electrode and repelling secondary electrons from said electrode, and deriving from said last stage successive groups of picture signals of a polarity that is periodically reversed in s'ynchronism with the rate of change of the potential supplied to said'electrode.

13. The method of transmitting and receiving television pictures in relief comprising the steps 0! projecting an optical "image of the object to be transmitted on a photosensitive member, deriving picture signals representative of said obiect from said member, reversing the polarity of successive groups of said picture signals at a predetermined frequency, transmitting said picture signals, receiving said picture signals, reproducing the television picture in accordance with said groups of picture signals in such a-manner to obtain a picture with positive transparency when a group of;signals of one polarity is reproduced and a succeeding picture with negative transparency when-the succeeding group of signals having the opposite polarity from that of said first group is reproduced, and' displacing said television pictures with positive transparency with respect to said television pictures with negative transparency, thereby to obtain a relief effect of the reproduced picture.

14. The method of transmitting and receiving relief pictures comprising the steps'of developing an electron beam, controlling saidbeaniiin accordance with received groups of picture, signals representative of the object tog be reproduced, each of said groups having "a signal polarity that is opposite from that of the succeeding group, deflecting said beam across a target-in accordance with cyclically recurring scanning field patterns to produce a luminous'image, and displacing the image representative of a group of picture signals of one polarity with respect to the image representative of the succeeding group-of picture signals of opposite polarity, thereby-to obtain a relief effect of the reproduced picture,

15. The method of transmitting television pictures in relief comprising the steps: of projecting an optical image of the object to be transmitted on a photosensitive member, deriving-picture signals representative of said object from said member. reversing the polarity of suceessiv'e'groupsof said picture signals at a predetermined frequency,

pulses, developing a fleld synchronizing signal including pulses of a frequency that is lower than that of said line synchronizing signal, developing a blanking signal including pulses of the same frequency as that of said line synchronizing signal, cyclically changing the time delay between the beginning of each pulse of said blanking signal and the beginning of each pulse of said line synchronizing signal so that said time delay changes in synchronism with the reversal of the polarity of said groups of picture signals, and mixing said blanking and synchronizing signals with said groups of picture signals, thereby to derive a composite video signal output adapted for the reproduction of television pictures having a relief efiect representative of said object.

16. A television system for transmitting and receiving relief pictures comprising a picture signal generating tube having means for deriving successive groups of picture signals representative of an object, means for transmitting said groups of picture signals, means for receiving said groups of picture signals, means for reproducing successive complete television images in accordance with said successive groups of picture signals, and means for periodically displacing one of said television images with respect to another one of said television images.

17. In a television system for receiving relief pictures, a cathode ray picture reproducing tube including means for developing an electron beam and a target adapted to be scanned by said beam, means for controlling said beam in accordance with received successive groups of picture signals, each group being representative of a complete image of the object'to be reproduced, means for deflecting said beam across said target in accordance with cyclically recurring scanning field patterns to produce successive complete luminous images, and means for periodically displacing one of said images representative of a group of said picture signals with respect to a succeeding image representative of another group of picture signals.

18. In a television system for receiving relief pictures, a cathode ray picture reproducing tube including means for developing an electron beam and a target adapted to be scanned by said beam, means for controlling said beam in accordance with received successive groups of picture signals representative of the object to be reproduced,

means for deflecting said beam across said target in accordance with cyclically recurring scanning field patterns to produce successive complete.

luminous images, said field patterns being synchronized with successive groups of picture signals, and means associated with said deflecting means for periodically displacing an image representative of a group of said picture signals with respect to the succeeding image representative of the succeeding group of said picture signals.

19. A television system for transmitting relief pictures including a picture signal generating tube having means for deriving successive groups of picture signals representative of an object, means .for developing a synchronizing signal including pulses, means for developing a. blanking signal .including pulses, means for cyclically changing the time delay between the beginning of each pulse of said blanking signal and the beginning of each pulse of said synchronizin signal. and means for mixing said blanking and synchronizing signals having their time delay 14 changed with said successive groups of picture signals to derive a composite video signal.

20. The method of transmitting and receiving television pictures in relief comprising the steps of deriving successive groups of picture signals representative of an object to be transmitted. transmitting said groups of picture signals, receiving said groups of picture signals, reproducing said successive groups of picture signals to obtain successive complete television images, and periodically displacing one of said television images with respect to another one ofsaid television images.

21. The method of receiving and reproducing relief pictures comprising the steps of developing an electron beam, controlling said beam in accordance with received successive groups of picture signals, each group being representative of a complete image of the object to be reproduced, deflecting said beam across a target in accordance with cyclically recurring scanning fleld patterns to produce successive complete luminous images, and periodically displacing one of said images representative of a group of picture signals with respect to a succeeding image representative of another group of picture signals.

22. The methodof transmitting television pictures in relief comprising the steps of deriving successive groups of picture signal representative of the object to be transmitted, developing a line synchronizing signal including pulses, developing a field synchronizing signal including pulses of a frequency that is lower than that of said line synchronizing signal, developing a blanking signal including pulses of the same frequency as that of said line synchronizing signal, cyclically changing the time delay between the beginning of each pulse of said blanking signal and the beginning of each pulse of said line synchronizing signal, and mixing said blanking and synchronizing signals having their time delay changed with said groups of picture signals to derive a composite video signal.

23. The method of receiving and reproducing relief pictures comprising the steps of developing an electron beam, controlling said beam in accordance with received successive groups of picture signals representative of the object to be reproduced, deflecting said beam across a target in accordance with cyclically recurring scanning fleld patterns to produce successive complete luminous images, and periodically displacing one of said images representative of a group of picture signals with respect to a succeeding image representative of another group of picture signals.

CHRISTIAN C. LARSON. CLYDE E. HALLMARK,

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,093,157 Nakashima et a1. Sept. 14, 1937 2,195,863 Knlck Apr. 2, 1940 2,386,087 Bingley et a1. Oct. 2, 1945 2,232,190 Vance Feb. 18, 1941 2,257,942 Farnsworth Oct. 7, 1941 2,029,103 Harvey Jan. 28, 1936 2,307,188 Bedford Jan. 5, 1943 2,281,891 Terry May 5, 1942 

